159 lines
7.9 KiB
Plaintext
159 lines
7.9 KiB
Plaintext
$FreeBSD$
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--------
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Vixie Cron Changes from V2 to V3
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Paul Vixie
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29-Dec-1993
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The crontab command now conforms to POSIX 1003.2. This means that when you
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install it, if you have any "crontab" command lines floating around in shell
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scripts (such as /etc/rc or /etc/rc.local), you will need to change them.
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I have integrated several changes made by BSDi for their BSD/386 operating
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system; these were offerred to me before I started consulting for them, so
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it is safe to say that they were intended for publication. Most notably,
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the name of the cron daemon has changed from "crond" to "cron". This was
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done for compatibility with 4.3BSD. Another change made for the same reason
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is the ability to read in an /etc/crontab file which has an extra field in
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each entry, between the time fields and the command. This field is a user
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name, and it permits the /etc/crontab command to contain commands which are
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to be run by any user on the system. /etc/crontab is not "installed" via
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the crontab(1) command; it is automatically read at startup time and it will
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be reread whenever it changes.
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I also added a "-e" option to crontab(1). Nine people also sent me diffs
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to add this option, but I had already implemented it on my own. I actually
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released an interim version (V2.2, I think) for limited testing, and got a
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chance to fix a bad security bug in the "-e" option thanks to XXX.
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The daemon used to be extraordinarily sloppy in its use of file descriptors.
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A heck of a lot of them were left open in spawned jobs, which caused problems
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for the daemon and also caused problems with the spawned jobs if they were
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shell scripts since "sh" and "csh" have traditionally used hidden file
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descriptors to pass information to subshells, and cron was causing them to
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think they were subshells. If you had trouble with "sh" or "csh" scripts in
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V2, chances are good that V3 will fix your problems.
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About a dozen people have reminded me that I forgot to initialize
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"crontab_fd" in database.c. Keith Cantrell was the first, so he gets the
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point.
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Steve Simmons reminded me that once an account has been deleted from the
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system, "crontab -u USER -d" will not work. My solution is to suggest to
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all of you that before you delete a user's account, you first delete that
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user's crontab file if any. From cron's point of view, usernames can never
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be treated as arbitrary strings. Either they are valid user names, or they
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are not. I will not make an exception for the "-d" case, for security
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reasons that I consider reasonable. It is trivial for a root user to delete
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the entry by hand if necessary.
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Dan O'Neil reminded me that I forgot to reset "log_fd" in misc.c. A lot of
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others also reminded me of this, but Dan gets the point. I didn't fix it
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there, since the real bug was that it should have been open in the parent.
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Peter Kabal reminded me that I forgot to "#ifdef DEBUGGING" some code in
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misc.c. Hans Trompert actually told me first, but Peter sent the patch so
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he gets the point.
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Russell Nelson told me that I'd forgotten to "#include <syslog.h>" in misc.c,
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which explains why a lot of other people complained that it wasn't using
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syslog even when they configured it that way :-). Steve Simmons told me
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first, though, so he gets the point.
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An interim version of the daemon tried to "stat" every file before
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executing it; this turned out to be a horribly bad idea since finding the
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name of a file from a shell command is a hard job (that's why we have
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shells, right?) I removed this bogus code. Dave Burgess gets the point.
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Dennis R. Conley sent a suggestion for MMDF systems, which I've added to the
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comments in cron.h.
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Mike Heisler noted that I use comments in the CONVERSION file which are
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documented as illegal in the man pages. Thanks, Mike.
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Irving Wolfe sent me some very cheerful changes for a NeXT system, but I
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consider the system itself broken and I can't bring myself to #ifdef for
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something as screwed up as this system seems to be. However, various others
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did send me smaller patches which appear to have cause cron to build and run
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correctly on (the latest) NeXT machines, with or without the "-posix" CFLAG.
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Irving also asked for a per-job MAILTO, and this was finally added later when
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I integrated the BSD/386 changes contributed by BSDi, and generalized some of
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the parsing.
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Lots of folks complained that the autogenerated "Date:" header wasn't in
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ARPA format. I didn't understand this -- either folks will use Sendmail and
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not generate a Date: at all (since Sendmail will do it), or folks will use
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something other than Sendmail which won't care about Date: formats. But
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I've "fixed" it anyway...
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Several people suggested that "*" should be able to take a "/step". One person
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suggested that "N/step" ought to mean "N-last/step", but that's stretching things
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a bit far. "*/step" seems quite intuitive to me, so I've added it. Colin Plumb
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sent in the first and most polite request for this feature.
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As with every release of Cron, BIND, and seemingly everything else I do, one
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user stands out with the most critical but also the most useful analysis.
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Cron V3's high score belongs to Peter Holzer, who sent in the nicest looking
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patch for the "%" interpretation problem and also helped me understand a
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tricky bit of badness in the "log_fd" problem.
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agulbra@flode.nvg.unit.no wins the honors for being the first to point out the
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nasty security hole in "crontab -r". 'Nuff said.
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Several folks pointed out that log_it() needed to exist even if logging was
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disabled. Some day I will create a tool that will compile a subsystem with
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every possible combination and permutation of #ifdef options, but meanwhile
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thanks to everybody.
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job_runqueue() was using storage after freeing it, since Jordan told me back
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in 1983 that C let you do that, and I believed him in 1986 when I wrote all
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this junk. Linux was the first to die from this error, and the Linux people
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sent me the most amazing, um, collection of patches for this problem. Thanks
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for all the fish.
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Jeremy Bettis reminded me that popen() isn't safe. I grabbed Ken Arnold's
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version of popen/pclose from the ftpd and hacked it to taste. We're safe now,
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from this at least.
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Branko Lankester sent me a very timely and helpful fix for a looming security
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problem in my "crontab -e" implementation.
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--------
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Vixie Cron Changes from V1 to V2
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Paul Vixie
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8-Feb-1988
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Many changes were made in a rash of activity about six months ago, the exact
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list of which is no longer clear in my memory. I know that V1 used a file
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called POKECRON in /usr/spool/cron to tell it that it was time to re-read
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all the crontab files; V2 uses the modtime the crontab directory as a flag to
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check out the crontab files; those whose modtime has changed will be re-read,
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and the others left alone. Note that the crontab(1) command will do a utimes
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call to make sure the mtime of the dir changes, since the filename/inode will
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often remain the same after a replacement and the mtime wouldn't change in
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that case.
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8-Feb-88: made it possible to use much larger environment variable strings.
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V1 allowed 100 characters; V2 allows 1000. This was needed for PATH
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variables on some systems. Thanks to Toerless Eckert for this idea.
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E-mail: UUCP: ...pyramid!fauern!faui10!eckert
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16-Feb-88: added allow/deny, moved /usr/spool/cron/crontabs to
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/usr/lib/cron/tabs. allow and deny are /usr/lib/cron/{allow,deny},
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since the sysv naming for this depends on 'at' using the same
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dir, which would be stupid (hint: use /usr/{lib,spool}/at).
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22-Feb-88: made it read the spool directory for crontabs and look each one
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up using getpwnam() rather than reading all passwds with getpwent()
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and trying to open each crontab.
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9-Dec-88: made it sync to :00 after the minute, makes cron predictable.
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added logging to /var/cron/log.
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14-Apr-90: (actually, changes since December 1989)
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fixed a number of bugs reported from the net and from John Gilmore.
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added syslog per Keith Bostic. security features including not
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being willing to run a command owned or writable by other than
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the owner of the crontab 9not working well yet)
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